Epithelial cells act as the most proximal arm of the innate immune system by sensing bacterial products and recruiting neutrophils to mucosal surfaces. During colonization, these cells are concurrently exposed to a vast array of microbial products, and it is not well understood how these combinations may alter the responses of epithelial cells. Preliminary data presented here describe a novel system for the generation of inflammation in the setting of polymicrobial stimulation. Concurrent exposure to two important human respiratory pathogens, S. pneumoniae and H. influenzae, induces synergistic production of proinflammatory cytokines by epithelial cells. This effect occurs both in vitro and in vivo and is associated with neutrophil recruitment. This proposal is designed to characterize the mechanism of this response. The first specific aim will address the hypothesis that specific bacterial components from S. pneumoniae and H. influenzae are necessary and sufficient for synergistic induction of inflammation. The second specific aim addresses specific host molecular mechanisms involved in this pathway. These studies have the potential to further the current understanding of immune responses at colonized mucosal surfaces, with implications for both colonization and invasive disease. [unreadable] [unreadable] This application describes a program designed to provide Dr. Adam Ratner with the skills necessary to become an independent investigator in microbial pathogenesis. Dr. Ratner has completed fellowship training in pediatric infectious diseases and will be mentored by Dr. Jeffrey Weiser, an expert in the pathogenesis of respiratory diseases. The program includes didactic study in the areas of genetics, immunology, and bacterial pathogenesis. In addition, an in-depth laboratory experience will expose Dr. Ratner to a wide variety of techniques in the areas of cell biology, biochemistry, physiology, and molecular biology, thus providing a solid foundation for beginning an independent research career. [unreadable] [unreadable] [unreadable]